Wireless communications devices such as the BlackBerry® by Research in Motion Limited enable users to download map content from web-based data sources such as BlackBerry Maps™ or Google Maps™. In the case of BlackBerry Maps™, the map data is in vector format, meaning that parks, lakes, oceans, islands, land masses, etc. are represented with polygons while highways, streets, railroads, etc. are represented with polylines. Mathematically, polygons and polylines are sets of coordinate points (the points being defined in terms of latitude and longitude).
When a user wishes to view a map on his or her wireless communications device, the user selects a location or area of interest (AOI) which triggers a request by the client device to the map server for the map data corresponding to the specific area or location requested by the user. The server retrieves the map data and sends the map data back to the client device to enable the device to dynamically render the map using the received map data. In the context of BlackBerry Maps™, the server first replies with an index of all available map data for the area of interest (AOI) which enables the device to select only those aspects of the map data it requires, thus economizing wireless bandwidth. Despite the use of this indexing technique for reducing over-the-air data transmission, the amount of data that is transmitted for an area of interest may still be very large. Particularly, when the user requests a map at a high zoom level (e.g. 10 km×10 km or greater), the amount of vector data being transmitted is excessive given the low level of detail being sought, i.e. only a fraction of all of the map data actually being transmitted to the wireless device is actually used in rendering the map. For example, as depicted in FIG. 1, a large-scale map of central North America shows not only the five Great Lakes but also myriad smaller lakes, providing a level of detail that most users do not necessarily require or expect. Downloading all this “extraneous” map vector data unnecessarily burdens the wireless link without providing any real benefit to user. Likewise, as depicted in FIG. 2, a map showing a highway interchange with on-ramps, exit ramps and service roads, may provide excessive detail for a user requesting a map at that zoom level. Furthermore, at that zoom level, the roads may appear to overlap, thus confusing the user and posing problems for on-screen labelling.
Accordingly, a technique for more optimally distributing map data content to wireless communications devices remains highly desirable.
It will be noted that throughout the appended drawings, like features are identified by like reference numerals.